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Question 14/12: Effects of interworking between multiple IP domains on the transmission performance of VoIP and voiceband services

(New question)

Type of question

Task oriented designed to lead to new ITU-T Recommendation(s).

Background

Various mechanisms like RSVP or MPLS are being introduced into IP networks to support voice over IP and other applications. The motivation, for example, for VoIP over MPLS is to take advantage of these new network capabilities, in those IP domains in the network where they are available, in order to improve voice over IP service by:

  • using label-switched-paths as a bearer capability for VoIP thereby providing more predictable, and even constrained QoS,
  • providing a more efficient transport mechanism for VoIP possibly using header compression or suppression,
  • using other advantages of MPLS, e.g. Layer 2 independence, integration with IP routing and addressing, etc.

The advantages of such mechanisms for the delivery of satisfactory end-to-end speech transmission performance can be understood in a single-domain environment with one specific mechanism deployed.

Today quite unpredictable, however, is the level of speech transmission performance through a concatenation of multiple IP domains which individually deploy different mechanisms.

The deployment of multiple VoIP islands interworking via the conventional PSTN will be a natural consequence of switch deployment practice:

  • A network or service provider might wish to deploy VoIP as a PSTN replacement to deliver PSTN-type voiceband services such as speech, facsimile and voiceband data.
  • A network or service provider might wish to deploy VoIP as a new type of voice service.
  • This will lead to multiple VoIP islands within a single carriers' network as well as islands which arise due to calls which are routed through multiple operators.
  • If deployment is driven by growth and obsolescence then the transition to a full VoIP solution will take 15 to 20 years, during which time multiple islands will be the normal situation.
  • Solutions which lead to retrofit requirements in order to solve QoS problems, are very unlikely to be cost effective.

It is possible to avoid excessive numbers of islands by deploying equipment and planning routing intelligently. Therefore, to enable operation with such network configurations it will be necessary provide appropriate Recommendations.

Text of the question

considering

a) that IP telephony connections may employ a multitude of IP domains;

b) that various signalling, routing and prioritization schemes can be deployed in each of such IP domains;

c) that end-to-end speech transmission performance of connections comprising of multiple IP domains will strongly depend on the interworking of signalling, routing and prioritization schemes between different IP domains;

d) that the deployment of VoIP equipment may be driven by growth and obsolescence and

e) that the transition to a full VoIP solution may take 15 to 20 years, during which time multiple VoIP islands in the PSTN will be the normal situation,

the following question should be studied:

- What are the conditions of interworking between multiple IP domains that need to be satisfied in order to deliver satisfactory end-to-end speech transmission performance and performance of other voiceband services?

Study items

a) The effects of interworking between multiple IP domains on VoIP speech transmission performance;

b) The effects of interworking between multiple IP domains on the transmission performance of voiceband services;

c) Deployment strategy: how to avoid excessive numbers of VoIP islands by deploying equipment and planning routing intelligently.

Objectives and schedule

It is anticipated that the study will result in new ITU-T Recommendation(s).

The estimated time frame is less than one Study Period.

Relationship with other activities

  • With other ITU-T Study Groups: SGs 2, 9, 11, 13, 16 (and maybe 4 and 15), SSG
  • With other Bodies: ETSI EP TIPHON, ETSI TC STQ, TIA TR-41, IETF

 

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